The first known use of cause of action was
in the 15th century

Legal Definition of cause of action

1: the grounds (as violation of a right) that entitle a plaintiff to bring a suit
an amended pleading reiterating a cause of action for lost profits— J. H. Friedenthal et al.also: the part of a suit brought on those grounds removed the cause of action to the district court

2: right of actionsense 1the court, led by Justice Brennan, said Congress intended to provide a private cause of action — National Law Journal